This invention relates to solenoid controlled, pilot operated inlet water valves and more specifically to water valves used in household appliances such as dishwashers and clothes washing machines.
Contamination, especially in the form of particulate matter, can impair the operation or clog water valves. Contamination can take many forms including sand particles, mineral particles, organic particles, mineral deposits, or other impurities. The basic structure of a pilot actuated water valve provides many opportunities for contamination to impair valve operation. There are small passages through which water must pass such as an inlet screen, bleed passage and a pilot passage. There are also close fitting parts that must move or seal such as the fitting between the pilot valve outlet extension and the outlet and the seal between the diaphragm and valving surface.
A water valve impairment can also take many forms including the following: a complete bleed passage obstruction causing catastrophic valve failure; a partial bleed passage obstruction slowing valve closing thereby wasting water; an obstruction between the outlet and the pilot valve outlet extension causing valve failure; a partial obstruction between the outlet and the pilot valve outlet extension causing slowed or incomplete valve closing; an obstruction between a guide tube and armature that causes valve failure; or a partial obstruction between the guide tube and armature that interferes with pilot valve operation.
An impaired water valve often increases water consumption through incomplete or slow closing. When an inlet water valve used in a household appliance is impaired but still functional, it may be difficult for the appliance operator to recognize the impairment because the water valve will leak to a holding tank or to a drain which may not be visible to the appliance operator. If the water valve is impaired by closing more slowly than designed, then water levels may be higher than desired or water volume may be greater than desired or the water valve may direct some water directly into an open drain. Unnecessary water consumption is not desirable, particularly when the water wasted is hot water. Wasting of even small amounts of hot water increases energy consumption.
In prior art appliance inlet water valves 20P, such as shown in FIG. 1, a bleed passage 28P is provided in a main valve 24P to allow pressure equalization between a main chamber 60P and an actuation chamber 58P. The bleed passage 28P is open when the main valve 24P is both open and closed. Since the bleed passage 28P is typically small, it is one of the most vulnerable valve structures to clogging. Additionally if contamination passes through the bleed passage 28P into the actuation chamber 58P, an armature 76P that slides in a guide tube 48P to operate the pilot valve 26P can become jammed causing main valve 24P failure.
Pressure equalization between the main chamber 60P and actuation chamber 58P is necessary in pilot actuated valves to provide assistance in closing the main valve 24P. Once the main valve 24P is open, pressure equalization is generally not required until the armature 76P closes the pilot valve 26P and pressure equalization is needed to close the main valve 24P. During the time the main valve 24P is open, the greatest pressure differential between the main chamber 60P and the actuation chamber 58P exists, so there is also the greatest flow rate through the bleed passage 28P. The pressure differential is caused by the outlet 38P vacuum being pulled into the actuation chamber 58P through the pilot valve outlet extension 82P.
Previous appliance water valves have decreased bleed passage clogging and armature jamming from contaminates with a lever operated bleed valve to decrease water flow through the bleed passage when the main valve is open. A lever operated bleed valve adds additional mechanical components that can fail, increases production costs, and can create a greater number valves that fail to meet quality standards. An example of a lever operated bleed valve is disclosed in U.S. Pat. No. 5,090,441 issued to Richmond.
Previous appliance water valves have also decreased bleed passage clogging and armature jamming from contaminates with a fine mesh inlet screen. A fine inlet screen is capable of preventing some contamination from entering the water valve, but the inlet screen itself can become clogged causing valve failure. Of course an inlet screen would not appreciably decrease water flow through the bleed passage, so contamination that could pass through the inlet screen could still become clogged in the bleed passage or enter into the actuation chamber and hinder valve operation.
Previous appliance water valves have decreased bleed passage clogging and armature jamming from contaminates by reducing the vacuum drawn from the outlet through the pilot valve outlet extension into the actuation chamber when the main valve is open. By reducing vacuum drawn into the actuation chamber, water flow through the bleed passage is reduced. Vacuum reduction is achieved by shortening the pilot valve outlet extension and reducing or eliminating its function of guiding the main valve onto a valving surface. Elimination of pilot valve outlet extension's guiding function can cause the main valve to seat in different positions on the valving surface. Since the main valve seat develops a seating groove, failure to seat in this groove can cause an incomplete seal. An example of a shortened pilot valve outlet extension is disclosed in U.S. Pat. No. 3,872,878 issued to Kozel et al.
Previous appliance water valves have also decreased bleed passage clogging and armature jamming from contaminates by gradually widening the bleed passage in the direction of water flow from the main chamber to the actuation chamber, so contamination that enters the bleed passage is less likely to be retained in the bleed passage. An example of a gradually widening bleed passage is disclosed in U.S. Pat. No. 4,500,067 issued to Zukausky.
Previous appliance valves have decreased pilot valve outlet extension jamming or sticking in the outlet caused by contaminates by reducing much of the exterior of the pilot valve so only a small portion of the pilot valve exterior adjacent to the downstream end fits closely within the outlet. An example of a pilot valve outlet extension with a reduced exterior is disclosed in U.S. Pat. No. 4,500,067 issued to Zukausky.
For the foregoing reasons, there is a need to reduce water flow and thereby contaminate flow through the bleed passage while the main valve is fully open to reduce the probability of the bleed passage becoming obstructed or the armature sticking or jamming in the guide tube. There is also a need to structure the bleed passage so that contaminates that enter the bleed passage pass through and do not obstruct the bleed passage. There is also a need to structure the bleed passage to decrease the likelihood of contaminates becoming lodged between the bleed passage entrance and the main valve diaphragm. Finally, there is a need to decrease the portion of the pilot valve outlet extension that fits closely in the outlet to decrease contaminate interference with the pilot valve extension while still maintaining the pilot valve extension guide function for proper valve operation.